Ink jet print heads for aqueous inks use multiple strategies for mitigating issues caused by ink drying within individual jet orifices. Ink jet print heads typically rely upon a stack of plates referred to as a jet stack, the final plate of which has an array of nozzles, also referred to as jets. When ink dries in the jet stacks or the nozzles, it causes artifacts in the resulting prints. Jets that receive a firing waveform to cause them to jet ink onto a substrate will fail to print when there is dried ink in the nozzle.
One common technique, called pre-fire or non-fire, energizes jets with a waveform of sufficiently low energy to avoid ejecting a drop of ink. These low energy waveforms serve to mix the dried high viscosity ink inside the nozzles with the bulk lower viscosity ink of the outlet chambers in the jet stack. Pre-fire waveforms typically drive a jet when the jet has not fired, or ejected ink, for some time but will fire in the near future.
Some existing systems send two bits of data to each jet for each pixel position. One bit indicates if a waveform should be driven to the jet or not. The other bit selects between a full energy, drop ejecting waveform, or a low energy pre-fire waveform. This method works well, but doubles the data bandwidth from the processor to print head, relative to a system without pre-fire capability. Techniques that do not require such high bandwidth will improve the operation of these printing systems.